1. Field of the Invention
The invention relates to a method for producing a charge control agent and a toner containing such charge control agent.
2. Description of the Related Art
In the past, a charge control agent formed by an azo metal complex has been widely used under circumstances in which a developer toner is used for electrophotography. The charge control agent is used to form the toner (for example: Japanese patent publication No. 63-61347 bulletin, Japanese patent publication No. 2-16916 bulletin, Japanese patent publication No. 2002-53539 bulletin and patent No. 2531957 bulletin). In recent years, along with the expanded use of electrophotography, charge control agents have been used to form the toner in the field of light printing.
The printing speed in light printing is required to be fast. In the printing field in general, including in light printing, the printing process itself is not evaluated, but the printed images, that is, the prints, are evaluated. In the printing field, an image hard copy is required to have a stable picture quality for a long period of time.
To ensure that the printed image achieves stability during high-speed printing, the developer must mix and electrify the newly recharged toner within short periods of time. In high-speed printing, the recharge rate of the toner also takes place at high speed; however, if the toner is insufficiently charged, then the charge on the toner, which is used as the developer, is not uniform. An insufficiently electrified toner can cause problems associated with toner, such as the flying of the toner and formation of fog.
Long-term use of a developer results in variations in the usage environment of an image formation device, and these environmental variations can influence the chargeability of the toner used as the developer. The obtained images, especially all-black or half-tone images, can display problematic variations in toner concentration.
Charge control agent formed by azo metal complex generally adopts a method in which an azo compound provides the raw materials for synthesizing a metal complex. The complexing agent and reaction medium used for synthesizing the azo metal complex cannot completely removed from the charge control agent in this method and residual components exist. The azo metal complex is synthesized using chromic formate as the complexing agent. The reaction medium usually contains ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, and other organic solvents. Chromic formate generates formic acid, which irritates the skin, and ethylene glycol monoethyl ether and ethylene glycol monomethyl ether are potentially hazardous chemical substances. Therefore, from a safety perspective, the standard method for producing a charge control agent using an azo metal complex without ethylene glycol monoethyl ether or ethylene glycol monomethyl ether is in high demand.